: The specific aims include: 1) Test the role of SLB, a putative new co-activator in the regulation of prolactin transcription. 2) Evaluate the functional significance of the interaction of Pit-1 with CBP through the use of a genetic screen to identify mutations in the Pit-1 POU domain which disrupt bindind to CBP. 3) Determine if the cAMP and TRH signaling pathways lead to changes in the chromatin structure of the PRL gene. 4) Determine if stimulation of prolactin transcription involves changes in the recruitment of transcriptional co-activators or co-repressors and changes in histone modification. 5) Test the role that specific transcription factors, co-activators and co-repressors play in organizing the chromatin structure and transcriptional potential of the prolactin gene. This will involve chromatin reconstitution using an in vivo Xenopus oocyte system as well in vitro using a Drosophila embryo system.